Update on "Make CI error on inductor fallback when decomp is available"

Fixes #99446 

Remove the warning, as that annoyed end-users who don't know what to do about it.

Instead, try to hold the line by preventing any decomp from being added without making
the corresponding change to inductor's fallbacks.

Note: we probably still need to better document how to update inductor's decomps,
for now it's pretty much "go ask the inductor team for advice"

cc soumith voznesenskym penguinwu anijain2305 EikanWang jgong5 Guobing-Chen XiaobingSuper zhuhaozhe blzheng Xia-Weiwen wenzhe-nrv jiayisunx peterbell10 desertfire

[ghstack-poisoned]

torch/_dynamo/allowed_functions.py

@@ -146,7 +146,6 @@ def _is_allowed_module_prefix(obj):
             "torch._C.inductor.",
             "torch.fx.",
             "torch.distributed.fsdp.",
-            "torch.distributed.nn.functional",
         )
         allowed_modules_dot = tuple([x + "." for x in allowed_modules])
         module = inspect.getmodule(obj)